Tractor-trailer power brake system



March 1 1949. R, R, GUNDERSON 2,463,172

' TRoToR-TRAILER POWER BRAKE SYSTEM Filed Jan. 6, 1945 2 Sheets-Sheet l March 1, 1949. R. R. GuNDERsoN TRACTOR-TRAILER POWER BRAKE SYSTEM 2 sheets-sheet 2 Filed Jan. 6, 1945 01%./ WM) WN Patented Mar. 1, 1949 UNITED sTArEs rnrENr OFFICE TRACTOR-TRAILER POWER BRAKE SYSTEM Ralph R. Gunderson, Chicago, Ill. Application January 6, 1945, Serial No. 571,583

3 Claims. 1 This invention relates to hydraulic brake systems and more particularly to a system for operating the brakes of a motor truck and trailer.

The primary object of the invention is to provide an improved hydraulic brake system wherein 1 only two hose connections are required between the tractor and the trailer, and in case of breakage of either of the hoses the brakes may be set on the trailer by pressure in the other hose.

Another object of the invention is to provide an improved power unit, including a suction motor booster, for the trailer brakes.

Another object of the invention is to provide an improved power unit, including a suction booster for the trailer brakes, wherein the valve to the booster will be controlled normally by the pressure from the pedal actuated master cylinder of the tractor, but in an emergency the same valve may be controlled by a hand valve on the tractor or automatically by a relay valve on the trailer.

Another object of the invention is to provide an improved operating cylinder for the trailer brakes wherein the pressure on the fluid coming from the master cylinder is increased.

Still another object of the invention is to provide a liquid reservoir for the operating cylinder on the trailer, which will enable air to escape from the cylinder when the brakes are released and cause liquid to ll the space left by the air. Of course, said reservoir will be automatically closed when pressure is applied to the operating cylinder.

The invention is illustrated in a preferred embodiment, in the accompanying drawings, in which- Figure 1 is a longitudinal sectional View of the operating cylinder, suction booster motor and relay valve for a trailer; Fig. 1A, an enlarged fragmentary sectional view of the movable cylinder and piston; Fig. 2, a diagrammatic view oi a brake system for a tractor and trailer; Fig. 3, a fragmentary sectional view of the operating cylin der shown in Fig. 2, but in the position where pressure is applied to the brake cylinders; and Fig. 4, a vertical sectional view taken as indicated at line 4-4 of Fig. 1.

' One form of the improved brake system is illustrated diagrammatically in Fig. 2,` wherein a broken section line 5 separates the tractor side at the left from the trailer side at the right. A master cylinder 6, actuated vby a 4brake pedal 4l, is adapted to force brake liquid through a conduit 8 to the truckoperating cylinder 9, and by means of a communicating conduit I to a trailer operating cylinder II. The trailer has a socket connection I2 for a coupling hose I3, which is shown in my application Serial No. 556,138, led September 28, 1944, now Patent No. 2,393,679, issued January 29, 1946.

A suction booster motor I4 on the tractor assists the operating cylinder 9 in forcing liquid through the conduit I5 to the wheel brake cylinders of the tractor. An intake .manifold I6 on the tractor may be the source of suction for boththe tractor and trailer. A conduit Il, provided with a check valve I8, leads to a tractor suction reserve tank I9, which is connected to the booster motor by suction line 29. The suction motor 'I4 is shown and described in my Patent No. 2,406,328, issued August 27, 1946. `A suction line 2i is connected to the suction line I1, through a manually operable valve 22, which may shut off the line 2l from the suction line Il or admit air into said line 2l. The line 2l connects up with the trailer through a detachable hose connection 23 provided with a shut off cock 24.

The operating cylinder II on the trailer is provided with a suction booster motor 25, which is a duplicate of the motor I4 and is 4shown in detail in Figure 1. A conduit 26 froml the operating cylinder leads to the brake cylinders on the wheels of the trailer. A suction reserve tank 2l is provided on the trailer, and is connected to the main suction line 2| through a check valve 2B. A suction conduit 29 leads from the suction tank to the booster motor, and is normally controlled by a valve 39, but is provided with an emergency relay member .'iI, which is connected at `one side by a conduit 32 to the suction tank, and is connected on the other side to a conduit 33 to the main suction line 2|.

Referring now to the power unit on the trailer, shown in Fig. 1, a main operating cylinder 34 is mounted on the trailerland is provided onlitslow pressure side with an auxiliary cy1i`nderg3 5,',o,f slightly larger diameter, lwhich 'communicates with the master cylinder of the tractor by mearis of the conduit Hl. A liquid reservoir tank 36 is provided on the top side of the cylinder 34, and has the usual ller cap 3l. A port tu connects the reservoir to the rear portion of the cylinder 34.

A hollow piston 3Q is provided in the cylinder 34, andvforms a small cylinder 40 for a piston 4i, whichactuates a push rod 42 by a yielding coinpressonspring 43. A hollow multiple head piston 44 has one head in the auxiliary cylinder 35, and a smaller diameter head in the cylinder 3ft. The smaller piston head 45 is adapted to bear against the end of the piston 39 when the brakes are released, as shown in Figure 1. When pressure is applied'rirom the.master cylinder tothe. conduit Il), thepartswillinidve to the positiorrfillustrated in Fig. 3*and the head 45 will succeed the head of the piston 39 in holding closed the port 32) to.

the reservoir.

The 'suction booster motors'ndvalvi'ssiiriil'arel to thatshown in my Patent No. 2,406,328, issued August '27, 1946, and has a metal casing"`4`iwpro vided with a diaphragm 41;'Which.isfsecure'dftogr andioitcebrake liquid.Y through thefconduit. 26

th e- .wheel.; .is`4 thec way the:- -brakes are no rxnally, .operated from V-the tractor by; pressure on. the, foot ;pedal,. .1-.

moveinentlotthe Apedallis; stopped, atmos- :p'resstlie s1:i'r i`ng,'43..'v and shutfoill the suction line, Aandif. the-.piston ."1 is movingV tol the right under the, inuenc'eg of fthibooster, pressure willjbe reduced on the small piston., 4`|` andi will further facilitate thel closingmoveinentof the valve. As

the operatingI cylinders'. of'. thetractor and oi the Ntrailer are. each .connected .tothe master, cylin der, pedal" pressure 'effects theA simultaneous op,- eration of` both.v Thisoperationnf. a power cylin- Iescrfirled.irl my PtentNo. 2,406,3'28`,fissued `August 27%,l 11946;.

"sh, ldbge broken,.for air."admittedfthrough;.the

T 'epusiirtditfz slidestnrougntnediaphraem 1 of the diaphragm 51, as viewed in Fig. 1, through the conduit 33, and as suction would be exerted on the opposite side of the diaphragm 5T by the conduit 32 to the suction tank, the ring 53 would be moved to the right and the suction motor operated to set the brakes.

Thus it Will be understood that breakage of the main suction line 2l would set the brakes on the trailer automatically, or, should the conduit l0 to the master cylinder be broken, the operator may set the brakes on the trailer by means of the Valve 22.

The foregoing detailed description is given for clearness of understanding only, and no unnecessary;- limitations:v ,'should be understood therefrom, for s'ome modications will be obvious to those skilled in the art.

' I claim:

' 1." A.,hydraulic brake system for a tractor and trailer comprising: a pedal actuated master 'cylinder-on a tractor; an oper-ating cylinder on saidtractorhaving one end connected to said master cylinder and the other end to wheel cylinders-'of the tractor; a piston in said operating cylinder; a suction booster motor connected to said pistonfandi'ha'vingy a valve to-amain suction line" on thertractor, saidvvalve being normally controlled bythe pressureV in the master cylinder; an operating cylinderfon the-trailer having one;` end makingaf fluid connection with the master-cylinder'onthe tractor-'and the other end with wheel-cylinders onsaid; trailer; a piston in said last' mentionedcylinder; 'a suction-reserve tank on the'trailer connected through acheck Vvalve-to said lmain suction line offsaid tractor; asuction booster mot-or connected to the last mentioned pistonrandhaving a valve inl a suc-- tion'linefromfsaidreserve tank; meansffor actu ating said last mentioned valve the pressure :5 40 `inthe-masterfcylinder; andadditional means for onening-saidf-valve-upon. loss-of suction in the mainv suction line to. the ftank.

2. A hydraulicbrake system, for atractor and trailer comprising: a; pedal actuated master 2.3 cylinder onatractor Vfor operating the brakes of said' tractor; a cylinder on the trailer havingone end makingahuidv connection with said master cylinder. ofthe tractor 'and the other end making a, uid. connectionwith. the wheel-cylinders of f1 i said trailer; apistonin.saiddastmentioned cylinder; a .suction booster .motor connected to said piston; a suction reserve tank. on said trailer connectedto a main suction line on said tractor; a check valve Vbetween, said tank and. main suction line; a suction line. from the reserve tank to said Vbooster motor a valve in the vlast mentioned suction linel for controllingv the booster motor; pistonrneans `for 'operating said valve by the pressure in the master cylinder; and an emerwhen the suction pressure-'fails in the main suction line to the tractor.

3. A hydraulicbrakey system for a trailer comprising: a cylinder adapted to be connected at g. onezend to a pedalactuated-inaster cylinder of a tractor and connected at its opposite end to wheel-cylinders ofthe trailer; a piston in said iirstmentioned cylinder;. a suction booster motor connected tosaidpiston; asuction reserve tank connected through a check valve to a main suction line on the tractor; a'valvefor connecting said booster motor'with said. suction reserve tank; normal means for actuatingtheibooste'r valve includingl a small Vcylindencommunicating with .said master; c ylindenyafpistonsri-v said lastmerr- 6 tioned cylinder having a push rod for actuating said booster valve, and a small exible diaphragm REFERENCES CITED connected to said push rod having one side com- The following references are of record in the municating with atmosphere and the other side le of this patent: with said suction motor; and emergency means 5 UNITED STATES PATENTS for actuating said booster valve includmg a relay member provided with a iiexible diaphragm con- Number Name Date nected to the booster valve, one side of said dia- 2,215,732 Bragg et al Sept- 24, 1940 phragm being connected to the main suction line 2,305,633 ROkWell Dec 22, 1942 of the tractor and the other side being connected 1o 2,359,687 Stelzel 001% 3, 1944 to the suction reserve tank. 2,361,419 Schnell 00t- 31, 1944 RALPH R. GUNDERSON. 

